Generations of Computers: From First to Fifth Explained

                           GENERATIONS OF COMPUTER

• The computer has evolved from a large-sized simple calculating machine to a smaller but much more powerful machine.
• The evolution of computer to the current state is defined in terms of the generations of computer.
• Each generation of computer is designed based on a new technological development, resulting in better, cheaper and smaller computers that are more powerful, faster and efficient than their predecessors.
• Currently, there are five generations of computer. In the following subsections we will discuss the generations of computer in terms of
  i. The technology used by them (hardware and software),
  ii. Computing characteristics (speed, i.e., number of instructions executed per second),
  iii. Physical appearance, and
  iv. Their applications.          

                                     

                                First Generation (1946 to 1955)

Table: Technologies used in 1st Generation

Technology used	Vacuum Tubes
Input	Punched Cards
Output	Punched Cards
Language	Machine Language
Storage	Punched Paper Tape

Hardware Technology:
The first generation of computer used vacuum tubes for circuitry and magnetic drums for memory. The input to the computer was through punched cards and paper tapes. The output was displayed as paper tapes.

Software Technology:
The instructions were written in machine language. Machine language used 0’s and 1’s for coding of the instructions. The first generation computers could solve one problem at a time.

Computing Characteristics:
The computation time was in milliseconds.

Physical Appearance:
These computers were enormous in size and required a large room for installation.

Application:
They were used for scientific applications as they were the fastest computing device of their time. 

Table: Example of 1st Generation

Harvard Mark I (electromechanical) Whirlwind ENIAC EDSAC UNIVAC I, UNIVAC II, UNIVAC 1101 RCA BIZMAC NCR CRC 102A, NCR CRC 102D Honeywell Datamatic 1000 Burroughs E101, Burroughs 220 IBM models 604, 650 (drum memory), 701, 702, 704, 705, 709

• The first generation computers used a large number of vacuum tubes and thus generated a lot of heat.
• They consumed a great deal of electricity and were expensive to operate.
• The machines were prone to frequent malfunctioning and required constant maintenance.
• Since first generation computers used machine language, they were difficult to program.

                                           Second Generation (1956 to 1965)

Table: Technologies used in 2nd Generation

Technology used	Transistors
Input	Punched Cards
Output	Paper
Language	Assembly Language
Storage	Magnetic Cores

i. Hardware Technology: Transistors replaced the vacuum tubes of the first generation computers.

• Transistors allowed computers to become smaller, faster, cheaper, energy efficient and reliable.
• The second generation computers used magnetic core technology for primary memory.
• They used magnetic tapes and magnetic disks for secondary storage.
• The input was still through punched cards and the output using printouts.
• They used the concept of a stored program, where instructions were stored in the memory of computer.

ii. Software Technology: The instructions were written using the assembly language.

• Assembly language uses mnemonics like ADD for addition and SUB for subtraction for coding of the instructions.
• It is easier to write instructions in assembly language, as compared to writing instructions in machine language.
• High level programming languages, such as early versions of COBOL and FORTRAN were also developed during this period.

iii. Computing Characteristics:
The computation time was in microseconds.

iv. Physical Appearance:
Transistors are smaller in size compared to vacuum tubes, thus, the size of the computer was also introduced.

v. Application:
The cost of commercial production of these computers was very high, though less than first generation computers. The transistors had to be assembled manually in the second generation computers.

Table: Example of 2nd Generation

UNIVAC 1107, UNIVAC III RCA 501 Philco Transact S-2000 NCR 300 series Honeywell 800, 400 series General Electric GE 635, 645, GE 200 Control Data Corp. CDC 1604, 3600, 160A   LARC

                                                 Third Generation (1966 to 1975)

Table: Technologies used in 3rd Generation

Technology used	Integrated circuits
Input	Keyboard
Output	Monitor
Language	High Level Language
Storage	Improved Disk Storage

i. Hardware Technology: The third generation computers used the integrated circuit (IC) chips.

• In an IC chip, multiple transistors are placed on a silicon chip.
• Silicon is a type of semiconductor.
• The use of IC chip increased the speed and efficiency of computer, manifold.
• The keyboard and monitor were used to interact with the third generation computer, instead of the punched card and printouts.

ii. Software Technology: The keyboard and the monitor were interfaced through the operating system.

• Operating system allowed different applications to run at the same time.
• High-level languages were used extensively for programming, instead of machine language and assembly language.

iii. Computing Characteristics: The computation time was in nanoseconds.

iv. Physical Appearance: The size of these computers was quite small compared to the second generation computers.

v. Application: Computers became accessible to mass audience. Computers were produced commercially, and were smaller and cheaper than their predecessors.

Table: Example of 3rd Generation

Burroughs 6700, Control Data 3300, 6600, 7600 Honeywell 200 IBM System/360, System 3, System 7 NCR Century Series RCA Spectra 70 series UNIVAC 9000 series General Electric GE 600 series, GE 235

• The third generation computers used less power and generated less heat than the second generation computers.
• The cost of the computer reduced significantly, as individual components of the computer were not required to be assembled manually.
• The maintenance cost of the computers was also less compared to their predecessors. 

                                         Fourth Generation (1975 to present)

Table: Technologies used in 4th Generation

Technology used:	Very large scale Integrated circuits (VLSICs), Microprocessor
Input:	Keyboard/Mouse/Scanner
Output:	Monitor
Language:	High Level Language, Non procedural Language
Storage:	Hard disk

i. Hardware Technology: They use the Large Scale Integration (LSI) and the Very Large Scale Integration (VLSI) technology.

• Thousands of transistors are integrated on a small silicon chip using LSI technology.
• VLSI allows hundreds of thousands of components to be integrated in a small chip.
• This era is marked by the development of microprocessor.
• Microprocessor is a chip containing millions of transistors and components, and designed using LSI and VLSI technology.
• This generation of computers led to the development of Personal Computer (PC).
• Semiconductor memory replaced the earlier magnetic core memory, resulting in fast random access to memory.
• Secondary storage device like magnetic disks became smaller in physical size and larger in capacity.
• The linking of computers, is another key development of this era. T
• The computers were linked to form networks that led to the emergence of the internet.
• This generation also show the development of pointing devices like mouse, and handheld devices.

ii. Software Technology: Several new operating systems like the MS-DOS and MS-Windows developed during this time.

• This generation of computers supported Graphical User Interface (GUI). GUI is user-friendly interface that allows user to interact with the computer via menus and icons.
• High-level programming languages are used for the writing of programs.

iii. Computing Characteristics: The computation time is in picoseconds.

iv. Physical Appearance: They are smaller than the computers of the previous generation. Some can even fit into the palm of the hand.

v. Application: They became widely available for commercial purposes. Personal computers became available to the home user.

Table: Example of 4th Generation

IBM System 3090, IBM RISC 6000, IBM RT ILLIAC IV Cray 2 XMP  HP 9000

                                                Fifth Generation (Present and Next)

• The goal of fifth generation computers is to develop devices that respond to natural language input and are capable of learning and self-organization.
• The fifth generation computers use Super Large Scale Integrated (SLSI) chips that are able to store millions of components on a single chip.
• These computers have large memory requirements.
• This generation of computers used parallel processing. This allows several instructions to be executed in parallel, Instead of serial execution.
• Parallel processing results in faster processing speed.
• The Intel dual core microprocessor uses parallel processing.
• The fifth generation computers are based on Artificial Intelligence (AI).
• They try to simulate the human way of thinking and reasoning.
• Artificial Intelligence includes areas like Expert System (ES), Natural Language Processing (NLP), Speech recognition, voice recognition, robotics, etc.

To understand the evolution of computers, make sure you also read our What is a Computer?